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Higher iron levels linked to gestational diabetes

Researchers say the findings raise questions about routine iron supplementation

Ingrid Torjesen

Friday, 11 November 2016

Higher iron levels are associated with an increased risk of gestational diabetes in pregnant women, shows a study* published in Diabetologia (the journal of the European Association for the Study of Diabetes), raising questions about the use of routine iron supplementation during pregnancy.

The prospective study included 107 gestational diabetes mellitus (GDM) cases and 214 controls (matched on age, race/ethnicity, and gestational week of blood collection). Biomarkers of iron status, including plasma hepcidin, ferritin, and soluble transferrin receptor (sTfR) were taken four times and used to calculate the sTfR:ferritin ratio, which captures both cellular iron need and availability of body iron stores. Biomarkers were measures at gestational weeks 10-14, 15-26, 23-31 and 33-39. Statistical modelling was then used to calculate the odds ratio of GDM with iron status.

The authors found that women with both hepcidin and ferritin levels in the top quartile in the second trimester of pregnancy had around a 2.5 times increased risk of developing GDM compared with those in the bottom quartile. A similar relationship was seen with ferritin levels in the first trimester. The sTfR:ferritin ratio was inversely related to GDM risk.

The authors said that the findings indicated that higher maternal iron stores may play a role in the development of GDM starting as early as the first trimester. “These findings are of clinical and public health importance as they extend the observation of an association between high body iron stores and elevated risk of glucose intolerance among non-pregnant individuals to pregnancy, and raise potential concerns about the recommendation of routine iron supplementation among pregnant women who already have sufficient iron."

The authors suggested that iron may play a role in the development of GDM through several potential mechanisms. As a strong pro-oxidant, free iron can promote several cellular reactions that generate reactive oxygen species and increase the level of oxidative stress, oxidative stress induced from excess iron accumulation can cause damage to and death of pancreatic beta cells, which produce insulin, and consequently, contribute to impaired insulin synthesis and secretion. In the liver, high iron stores may induce insulin resistance via impaired insulin signalling, as well as by limiting the capacity of the liver to extract insulin.


* Rawal S, Hinkle SN, Bao W, et al. A longitudinal study of iron status during pregnancy and the risk of gestational diabetes: findings from a prospective, multiracial cohort. Diabetologia, 2016. DOI: 10.1007/s00125-016-4149-3

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